The Two-Way

4:55 pm

Wed June 12, 2013

Huge System Of Storms Predicted To March East From Midwest

A map shows the chance of severe thunderstorms Wednesday evening, with the National Weather Service predicting strong winds and storms moving eastward to the mid-Atlantic Thursday.

NOAA

The National Weather Service warns of a massive storm system that will make its way eastward from Iowa to Maryland in the next 24 hours, as strong winds, thunderstorms, and hail are predicted to hit areas from the upper Midwest to the Mid-Atlantic beginning Wednesday and continuing Thursday.

The weather service's Storm Prediction Center is predicting "widespread damaging winds and a few strong tornadoes" in parts of the middle Mississippi Valley, the upper Ohio Valley and lower Great Lakes area Wednesday evening. Driven by hot, humid air, the storms will head east in a pattern reminiscent of last summer's derecho storm.

The system "could affect one in five Americans on Wednesday," as the storm passes through one of America's most densely populated areas, the AP says.

Update at 8:30 p.m. ET. Funnel Clouds Reported:

As of 8:30 p.m. ET, more than 11,000 people in and around Chicago, Ill., are without power, after strong winds hobbled part of the electrical grid. Local utilities were adding more work crews to cope with outages, and the area is under a flood watch.

Those problems are not the worst that were predicted for Illinois and other states in the path of a massive storm system that is rolling eastward. While sightings of funnel clouds have been reported, The Chicago Tribune says they hadn't been confirmed early Wednesday evening.

"The area is seeing heavy rain, some hail and lots of lightning and thunder," the newspaper reports, "but there have not been any confirmed damage reports except for the Aurora Fire Department responding to two calls of apparent lightning strikes on electrical transformers. There were no fires to any structures, said Dan Ferrelli, city spokesman."

The Tribune also reports that about 100 flights have been cancelled at O'Hare International Airport.

In an afternoon update, WGN-TV meteorologist Tom Skilling said of the powerful thunderstorms that were forming just west of Chicago, "these things tower over 55,000 feet."

Multiple tornadoes were reported in Iowa, causing property damage. State officials say there have been no reported injuries or deaths from those incidents, the AP reports.

Our original post continues:

The storm center's meteorologists say that with time, the storms "are expected to develop into a fast-moving squall line with the primary threats being widespread damaging winds and embedded tornadoes. A few wind gusts in excess of 75 mph will be possible as the line of thunderstorms moves rapidly east across the southern Great Lakes and Ohio valley region this evening."

For many, that description — of a line of powerful winds moving across a broad swath of America — has brought to mind last summer's derecho, the name for a storm that moves in a straight line with wind gusts that hit at least 58 mph. Derecho wind speeds can soar well over that threshold; the strongest gusts recorded have exceeded 120 miles per hour.

To be deemed a derecho, the system would also have to cause damage across an area at least 240 miles wide.

Derechos are "notoriously difficult to forecast," the National Weather Service says. The storms also move quickly, leaving little time for those in its path to prepare themselves or move to safety. The derecho that struck last June was blamed for 13 deaths, along with power outages for 4 million people.

The Storm Prediction Center issued a tornado watch for parts of Iowa, Illinois, Minnesota, and Wisconsin late Wednesday, describing what it calls "a particularly dangerous situation."

The tornado watch was to remain in place for those areas until at least 9 p.m. CDT. Forecasters say that hail may be as wide as three inches across.